The present invention relates to optical fiber splicing apparatus integrated with an oven for heating a protective sleeve placed over the bare optical fibers in a finished splice, in particular for splicing optical ribbon fibers and ribbonized optical fibers.
In the fiber-optical communication technology to a higher and higher extent, in addition to loose or separate optical fibers, optical ribbon fibers or xe2x80x9cribbonsxe2x80x9d are used, i.e. optical fibers which by an outer enclosure are held to form a unit of type ribbon cable, i.e. a flat fiber assembly including a plurality of optical fibers extending in parallel to each other. Such a ribbon fiber typically contains 2, 4, 6, 8, or 12 individual fibers. Also ribbonized optical fibers are used which can be handled like ribbon fibers but which are retained at each other to form a unit in a less permanent way, see for example European patent application 00850042.3, filed Mar. 10, 2000. When splicing optical fibers and ribbon fibers often fusioning, also called welding or fusion-welding, is used in apparatus particularly designed for this purpose. When splicing two optical fibers to each other, thus the different enclosures and protective layers on the fibers are first removed. This can be made in a single step so that the naked surfaces of the optical fibers appear after the operation. Thereupon the naked fibers are cut off, are placed in the fiber splicing apparatus and are spliced to each other. Thereafter a separate protective sleeve is placed over the splicing region. Such protective sleeves are usually heat-shrinkable pieces of tubing made of a suitable polymer material. Such a piece of tubing is then placed over the spliced portions of the fibers and the protective sleeve and the spliced portions are moved to an oven, in which the protective sleeve is heated to make it shrink and tightly seal the spliced portions. The two operations, splicing using fusioning and applying the protective sleeve tightly around the spliced portions, are most often executed in two separate devices. Then, a manual displacement of the spliced fibers between these devices is used. Such a direct handling can be associated with different difficulties, in particular when moving ribbonized optical fibers, which are only kept together by adhesive tape pieces placed at a distance of each other. In addition, the non-protected spliced portions can be brittle after the splicing operation and can easily break. Therefore, a need exists for devices to facilitate the displacement of optical fibers between a splicing station and a heating station.
In U.S. Pat. No. 4,736,632 for Peter G. Case of BICC optical fiber splice mechanical testing apparatus for use with optical fiber splicing equipment is disclosed. The testing apparatus includes two clamping devices mounted on the splicing equipment located at spaced locations along the two optical fibers to be spliced, on opposite sides of the splicing position. One of the clamping devices is mounted to move towards or away from the other clamping device and is urged by a coil spring to a position remote from the splicing position. The movable clamping device can be temporarily maintained in a position nearer the splicing position when actually making the splice by operating a knob. The testing apparatus is also employed to transfer the spliced optical fibers from the splicing station to a station at which a heat-shrinkable plastics sleeve can be applied to the spliced portions of the fibers, without any manhandling of the spliced fibers by an operator. This device is not particularly suited for splicing and handling ribbon fibers and ribbonized fibers and particularly for use in splicing apparatus having a complicated design in which the simple swinging movement of the clamping devices and the held spliced fibers cannot be used.
It is an object of the invention to provide fiber splicing apparatus which includes an oven or other heating device for applying a protective sleeve around spliced fiber portions, in which the transport between the location in the apparatus where the splicing is made and the heating device can be made in a simple and secure way, in particular without any substantial risk of the occurrence of any break of the spliced fibers.
It is another object of the invention to provide a transport device for fiber splicing apparatus which can move, without the spliced fibers having to be touched by the hands of an en operator, the fibers to a heating place or other device to apply a protective sleeve.
Generally thus, splicing apparatus for optical fibers, which is particularly suited for splicing ribbonized optical fibers and also for optical fiber ribbons, has a splicing part for splicing the optical fibers to each other and a heating part or oven for heating a protective shrinkable sleeve to be fitted around the spliced portions of the optical fibers. A transport device is provided for transporting the spliced optical fibers from the splicing part to the heating part. The transport device comprises clamps at the sides of the frame of the splicing apparatus, which are elastically biased to give the spliced fibers a straight state between the clamps. The transport device is manually operated such as by a handle to lift the clamps and the optical fibers optical held thereby to be moved along a first, slightly path segment unobstructed by the different components of the splicing part. Thereafter a second handle can be operated to displace the clamps and thereby the optical fibers to move in a straight path, the clamps sliding along side rails having elongated holes, to a position having the spliced portions located at the heating part.
Owing to the path of the transport device and thus of the spliced optical fibers they do not have to be manually handled between the splicing operation and the application of a protective sleeve. Furthermore the fibers can be held having a rectilinear shape and somewhat tensioned over the spliced portions, what minimizes the risk of breaks of the individual optical fibers at the splice. Furthermore, the total time of splicing optical fibers to each other and applying a protecting sleeve can be reduced.
Thus, splicing apparatus for splicing optical fibers to each other generally comprises a splicing part having fiber guides and some fusion-splicing means for splicing optical fibers, a heating part for heating a protective sleeve placed over spliced portions of spliced optical fibers spliced to each other in the splicing part to make the protective sleeve shrink around the spliced portions tightly enclosing them, and a transport device for in a first position holding spliced fibers in a first position in the splicing part and for displacing the held optical fibers from the first position to a second position, in which spliced portions of the fibers are located at or are at least partly enclosed by the heating part, by transferring the transport device to a second position. The transport device has clamping devices to firmly hold the spliced fibers when transferring the transport device from the first to the second position.
Particularly, the transport device comprises mechanical guides to transfer the clamping devices from the first position of the transport device to the second position along a path including two substantially straight segments, a first segment and a second segment. The first and second segments meet in an angle to each other, this angle e.g. being in the range of 45-90xc2x0. Thus the path has a shape like an angle allowing the spliced fibers to be first lifted in a substantially perpendicular or vertical direction from the splicing part and then to be moved along a path from a top position in a sloping direction to the heating part. The first segment can be slightly curved such as being part of circle having a relatively large diameter in the magnitude order of the distance between the splicing and heating parts and having a center located somewhere close to the heating part. The second substantially straight segment can be completely straight.
The transport device can have side-rails at opposite sides of the splicing apparatus, which have elongated holes cooperating with the clamping devices to allow movement of the clamping devices along the second segment. The side-rails can then be rotatably mounted on the frame by bearings located at a first end of the elongated holes, the bearings corresponding to said center of the circle and placed to allow movement of the clamping devices along the first segment when rotating the side rails about the bearings. The transport device can advantageously comprise movement restricting means restricting the rotary movement of the side-rails about the bearings. The movement restricting means then may comprise a pin and a mechanical elongated guide cooperating with each other and can allow, by e.g. suitable design of the mechanical guide, the side-rails to temporarily rest in a lifted position to allow the movement along the second path.
The clamping devices are preferably elastically biased to impart, after releasing the optical fibers spliced to each other from the splicing part, a tensional force to the optical fibers to give them a substantially straight state. Locking means can cooperate with the clamping devices to hold them in inner positions, close to the splicing part, so that when opening the locking devices the clamping devices are released and move away from each other to give the fibers spliced to each other the substantially straight state. The locking means preferably comprise arms or levers having projections including engagement surfaces cooperating with surfaces of the clamping devices, the levers being mounted to rotate in planes substantially perpendicular to the longitudinal direction of spliced optical fibers held by the clamping devices and the engagement surfaces being located in relatively small angles, such as in the range of 2-15xc2x0, to the planes to allow, when rotating the levers when opening the locking devices, the clamping devices to move gradually away from each other, thereby avoiding a sudden increase of tensional force on the spliced optical fibers and possible breaks caused thereby.